Blended shaft drive

ABSTRACT

A solid, monolithic shaft member has an engagement end. The engagement end has a proximal end a distal end. The proximal end has a first cross-sectional geometry, and the distal end has a second cross-sectional geometry. The first cross-sectional geometry of the proximal end is different from the second cross-sectional geometry of the distal end. The cross-sectional geometry of the distal end transitions to the a cross-sectional geometry of the proximal end along a longitudinal axis of the engagement end of the solid, monolithic shaft member. This transition provides a gradual, blending, continuously transitioning cross-sectional geometry along the entire length of the longitudinal axis of the engagement end of the solid, monolithic shaft member.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. patent application Ser. No.13/276,920, filed on Oct. 19, 2011 and entitled “BLENDED SHAFT DRIVE,”the entirety of which is hereby incorporated herein by reference.

BACKGROUND

Shaft drive tools, generally, have insufficient torque carryingcapability and can fail under torsion loading. Specifically, shaft drivetools incorporate a drive feature that transitions rapidly to a basegeometry (usually a cylinder), and this rapid transition in geometrycreates a failure location at which stress risers accumulate and causecatastrophic failure under load. Occurrences of this type of failure areincreasingly likely as drive tools are narrowed for the delivery ofincreasingly smaller diameter fasteners. A need therefore exists for animproved shaft drive.

SUMMARY

One approach provides an improved blended shaft delivery device. Thedelivery device includes a solid, monolithic shaft member. The shaftmember has an engagement end. The engagement end has a proximal end anda distal end. The proximal end has a first cross-sectional geometry, andthe distal end has a second cross-sectional geometry. The firstcross-sectional geometry of the proximal end is different from thesecond cross-sectional geometry of the distal end. The cross-sectionalgeometry of the distal end transitions to the cross-sectional geometryof the proximal end along a longitudinal axis of the engagement end ofthe solid, monolithic shaft member. The transition provides a gradual,blending, continuously transitioning cross-sectional geometry along theentire length of the longitudinal axis of the engagement end of thesolid, monolithic shaft member.

In some examples, the cross-sectional geometry of the distal end is in ashape of at least one of a triangle, a square, a rectangle, a hex, acircle, an ellipse, a cross, and a torx. In some examples, thecross-sectional geometry of the proximal end is in a shape of at leastone of a triangle, a square, a rectangle, a hex, a circle, an ellipse, across, and a torx. In other examples, cross-sectional geometry of thedistal end of the delivery device is in a shape of a polygon.

In some examples, the solid, monolithic shaft member has no abrupttransitions in cross-sectional geometries along the longitudinal axis,and the cross-sectional geometry of at least one of the proximal end orthe distal end has a shape adapted to mate with a fastener cavity ofsubstantially the same shape. In some examples, the fastener cavityprovides a blending, continuously transitioning cross-sectional geometryalong the longitudinal axis of the cavity adapted for receiving theblending, continuously transitioning cross-sectional geometry of theengagement end of the solid, monolithic shaft. In other examples, thefastener cavity includes at least two different cross-sectionalgeometries.

In some examples, the engagement end of the delivery device has a yieldstrength ranging between 175,000 psi and 250,000 psi, and in otherexamples, the engagement end of the delivery device has a yield strengthis 220,022 psi.

Another approach is a fastening system. The fastening system includes asolid, monolithic shaft member having an engagement end. The engagementend has a proximal end and a distal end. The proximal end has a firstcross-sectional geometry, and the distal end has a secondcross-sectional geometry. The first cross-sectional geometry of theproximal end is different from the second cross-sectional geometry ofthe distal end. The cross-sectional geometry of the distal endtransitions to the cross-sectional geometry of the proximal end along alongitudinal axis of the solid, monolithic shaft member. The transitionprovides a gradual, blending, continuously transitioning cross-sectionalgeometry along the entire length of the longitudinal axis of theengagement end of the solid, monolithic shaft member. The fastenersystem includes a fastener defining a longitudinal cavity ofsubstantially the same shape as the cross-sectional geometry of at leastone of the proximal end or the distal end of the engagement end of thesolid, monolithic shaft.

In some examples, the cross-sectional geometry of the distal end is in ashape of at least one of a triangle, a square, a rectangle, a hex, acircle, an ellipse, a cross, and a torx. In some examples, thecross-sectional geometry of the proximal end is in a shape of at leastone of a triangle, a square, a rectangle, a hex, a circle, an ellipse, across, and a torx. In other examples, the engagement end of the solid,monolithic shaft member includes no abrupt transitions incross-sectional geometries along the longitudinal axis.

In some examples, the longitudinal cavity of the fastener provides ablending, continuously transitioning cross-sectional geometry along thelongitudinal axis adapted for receiving the blending, continuouslytransitioning cross-sectional geometry of the engagement end of thesolid, monolithic shaft. In some examples, the longitudinal cavityincludes at least two different cross-sectional geometries along thelongitudinal axis.

Another approach is a fastener for securing a suture. The fastenerincludes a body member having an exterior surface and defining aninterior cavity. The exterior surface includes a fixation element; andthe interior cavity includes a longitudinal cavity having a blending,continuously transitioning cross-sectional geometry along thelongitudinal axis of the body member. In some examples, the longitudinalcavity includes at least two different cross-sectional geometries. Insome examples, the longitudinal cavity is adapted for receiving anengagement end of a drive shaft having a cross-sectional geometry ofsubstantially the same shape as the longitudinal cavity. In someexamples, the exterior surface of the fastener further includes aretention element.

The blended shaft drive and fastening system described herein providesone or more of the following advantages. For example, one advantage ofthe blended shaft drive and fastening system is that the blended shaftdrive allows for the application of increased torsional strength duringfastener delivery, thereby enabling the blended shaft drive to secure afastener without breaking and thereby reducing costs and health risksrelated to removing and replacing broken shaft and fastener assembliesfrom a patient undergoing arthroscopic surgery. Another advantage of thetechnology is that the blended shaft drive allows for reduced fastenersize (i.e., reduced overall fastener implant size), thereby decreasingthe manufacturing cost for the technology by reducing materials,improving fastener deployment in low clearance areas, and/or minimizingphysical trauma to a recipient of the fastener. Another advantage of thetechnology is that the blended shaft drive allows for greater fixationstrength of the mating fastener (e.g., less implant volume dedicated toapplying torque allows for greater implant volume dedicated to fixationstrength), thereby improving likelihood of fastener retention whilereducing the overall cost and physical trauma to a recipient.

Other aspects and advantages of the current technology will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, illustrating the principles of thetechnology by way of example only.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of various examples of the technology will bemore readily understood by reference to the following detaileddescriptions in the accompanying drawings, in which:

FIG. 1A is a schematic illustration of a perspective view of a fasteningsystem, according to an illustrative example;

FIG. 1B is an enlarged bottom perspective view of a portion of thefastening system, according to the illustrative example of FIG. 1A;

FIG. 1C is a schematic illustration of a top perspective exploded viewof a portion of the fastening system, according to the illustrativeexample of FIG. 1A;

FIG. 1D is a schematic illustration of a bottom perspective explodedview of a portion of the fastening system, according to the illustrativeexample of FIG. 1A;

FIG. 1E is a schematic illustration of a top view of an assembledportion of the fastening system, according to the illustrative exampleof FIG. 1A;

FIG. 2 is a schematic illustration of a perspective view of a blendedshaft drive, according to an illustrative example;

FIG. 3A is a schematic illustration of a cross-sectional side view of ablended shaft drive mated with a fastener, according to an illustrativeexample;

FIG. 3B is a schematic illustration of a perspective end view of theexample of FIG. 3A cross-sectioned along line B-B;

FIG. 3C is a schematic illustration of a perspective end view of theexample of FIG. 3A cross-sectioned along line C-C;

FIG. 3D is a schematic illustration of a perspective end view of theexample of FIG. 3A cross-sectioned along line D-D;

FIG. 4 is a schematic illustration of a perspective view of a deliverydevice exhibiting stress concentrations under load, according to anillustrative example;

FIG. 5 is a schematic illustration of a perspective view of a prior artdelivery device exhibiting stress concentrations under load; and

FIG. 6 is a schematic illustration of a cross-sectional side view of afastener, according to an illustrative example.

DETAILED DESCRIPTION

The blended shaft drive includes components that enable the reliableaffixation of compact fasteners requiring secure placement in lowclearance and/or limited access areas. For example, one use of theblended shaft drive is for securing a device (anchor/fastener/suture)that connects tendon to bone without causing a patient unnecessaryphysical trauma otherwise caused by invasive arthroscopic procedures.Because tendons absorb and impart strong forces, the device must affixsuch tendons securely to bone to enable successful healing. In thisexample, secure affixation is achieved by a system of an anchor andfastener, a suture, and the blended shaft drive that deploys thefastener within an anchor for securing the suture attached to a tendon.Compared to legacy drive tools, the blended shaft drive is relativelynarrow for deploying a compact fastener that requires minimal clearanceand a relatively small area footprint in the bone. Because the blendedshaft geometry has no abrupt transitions, the relatively narrow blendedshaft drive withstands high torque forces (at least 3 in-lbf) withoutbreaking/failure.

FIGS. 1A through 1E depict an example of a fastening system 1000including a high strength delivery device 1010 and a two part footprintanchor 1050. FIG. 1A illustrates the assembled components of thefastening system 1000. FIG. 1B shows a exploded enlarged portion of thefastening system 1000 of FIG. 1A. FIGS. 1C and 1D show explodedperspective views of the exploded portion of FIG. 1B. FIG. 1E shows anexample of an enlarged schematic top view of assembled components of thefastening system 1000.

The delivery device 1010 includes an insertion handle 1015 and atwo-part insertion shaft 1020 having a hollow outer shaft 1030surrounding an inner, solid, monolithic shaft member 1025. The solid,monolithic shaft member 1025 is adapted for applying torque to anengaged fastener 1055. In some examples, the fastener 1055 requiresplacement within a receiving cavity of an outer body 1060 for securing asuture 1045 therebetween. The outer shaft 1030 engages with the outerbody 1060. For example, the delivery device 1000 could be one forengaging, delivering, and securing a suture fixation fastening systemfor use in arthroscopic procedures involving securing tissue to bone. Assome examples, the delivery device 1010 could be one for engaging,delivering and securing a fastener in any low-clearance assembly, suchas those forming components of aircraft, automobiles, and bicycles, allof which require high torque fasteners in densely populated areas.

With regard to the example of a suture fixation fastening system 1000,such a system requires application of high torque on the fastener 1055to secure a suture 1045 against the outer body 1060, which is securelydriven into a bore formed in a bone 1070. The two-part footprint anchor1050 thereby enables attachment of tissue (e.g., a tendon) to bone.Turning a torque limiter knob 1035 at the top of the inserter handle1015 transfers torque to the solid monolithic shaft member 1025. Theapplication of torque limiter knob 1035 enables the solid, monolithicshaft member 1025 to secure a fastener 1055 within the outer body 1060without over tensioning the fastener 1055. The delivery device 1010therefore secures strong tendon tissue to bone without the solidmonolithic shaft member 1025 breaking/failing under the application oftorsion force. This advantageously reduces costs and time otherwiseassociated with removing and replacing an assembly of the broken solid,monolithic shaft member 1025, the fastener 1055 and the suture 1045 frompatients during surgery. Withstanding high torque forces enables thedelivery device 1000 to deliver the fastener 1055 reliably, thereforedecreasing the risks associated with prolonged surgery. The solid,monolithic shaft member 1025 also allows for reduced fastener size(i.e., reduced overall fastener implant size), thereby decreasing themanufacturing cost for the technology by reducing materials, improvingfastener deployment in low clearance areas, and/or minimizing physicaltrauma to a recipient of the two part footprint anchor 1050. The solid,monolithic shaft member 1025 allows for greater fixation strength of themating fastener 1055 (e.g., less implant volume dedicated to applyingtorque allows for greater implant volume dedicated to fixationstrength), thereby improving the likelihood of fastener 1055 retentionwhile reducing the overall cost of manufacture of the fastening system1000.

FIG. 2 depicts a portion of an exemplary delivery device (e.g., deliverydevice 1010 of FIG. 1A), which includes a solid, monolithic shaft member2025 having an engagement end 2102 for driving a fastener (e.g. fastener3255 of FIG. 3A). In some examples, the solid, monolithic shaft member2025 is manufactured from a single, solid piece of stock (e.g., surgicalsteel, composite, etc.). The solid, monolithic shaft member 2025 can be,for example, a unitary, single-component body having no cavity therein.The engagement end 2102 of the solid, monolithic shaft member 2025 has aproximal end 2105 and a distal end 2110 for engaging with the fastener3255. The proximal end 2105 has a first cross-sectional geometry 2107and the distal end 2110 end has a second cross-sectional geometry 2112.The first cross-sectional geometry 2107 of the proximal end 2105 isdifferent from the second cross-sectional geometry 2112 of the distalend 2110. As illustrated in FIG. 2, the first cross-section geometry2107 of the proximal end 2105 is a circle and the second cross-sectiongeometry 2112 of the distal end 2110 is a triangle with flattenedcorners 2114. The flattened corners 2114 can prevent any concentrated,localized applications of force that would create potential modes offailure. Sharp corners on an engagement end can lead to potentialcracking and/or fatiguing of a mated fastener during application oftorque, thereby causing health risks and trauma associated withprolonging surgery to remove and replace a fastener and any deployedsuture which has already been attached to the tissue requiringaffixation to bone.

The second cross-sectional geometry 2112 of the distal end 2110transitions to the first cross-sectional geometry 2107 of the proximalend 2105 along a longitudinal axis 2115 of the engagement end 2102 ofthe solid, monolithic shaft member 2025. The transition provides agradual, blending, continuously transitioning cross-sectional geometryalong the entire length of the longitudinal axis 2115 of the engagementend 2102 of the solid, monolithic shaft member 2025. The firstcross-sectional geometry 2107 of the proximal end 2105 thereforetransitions into the second cross-sectional geometry 2112 of the distalend 2110 without any abrupt transitions that would trigger theaccumulation of stress risers (i.e., areas of concentrated stress) thatcould lead to catastrophic yield or breakage. A rapid transition ingeometry (i.e., a geometric discontinuity) weakens an object becauseforce is not evenly distributed over the object. Instead, localizedincreases in stress occur when an abrupt transition in geometry occurs.By smoothly and progressively transitioning from one cross-sectionalgeometry to another along the longitudinal axis 2115 of the engagementend 2102, the solid, monolithic shaft 2025 eliminates rapid transitions,such as tapers and undercuts, and therefore eliminates rapid physicalchanges that induce stress risers. The smooth and progressive transitionadvantageously enables the application of high torque without the riskof breaking apart the solid, monolithic shaft 2025 and requiring costlyand risky extraction and replacement of the fastener 3255 and suture(not shown).

In some examples, the cross-sectional geometry of the distal end 2110 isin a shape of at least one of a triangle, a square, a rectangle, a hex,a circle, an ellipse, a cross, and a torx, for example. In someexamples, the cross-sectional geometry of the proximal end 2105 is in ashape of at least one of a triangle, a square, a rectangle, a hex, acircle, an ellipse, a cross, and a torx, for example. In other examples,the cross-sectional geometry of the distal end 2105 is in a shape of apolygon, the sides thereof providing sufficient contact with a fastener(e.g. 3255 of FIG. 3A) such that an application of torque on the solid,monolithic shaft 2025 drives the engaged fastener 3255. In yet someexamples, a torque application end 2120 includes at least a thirdcross-sectional geometry (not shown). In examples, any number ofcross-sectional geometries is contemplated such that the transitionsbetween geometries are progressive and no abrupt transitions in geometryexist. Although the distal end 2110 and the proximal end 2105 aredescribed as being one of a listed shape, the distal end 2110 and/or theproximal end 2105 can be any shape and/or any combination of shapes(e.g., square to diamond, torx to circle, rectangle to octagon, etc.)

In some examples, the cross-sectional geometry of at least one of theproximal end 2105 or the distal end 2110 has a shape adapted to matewith a fastener cavity (e.g. 3215 of FIG. 3A) of substantially the sameshape. In some examples, the fastener cavity provides a blending,continuously transitioning cross-sectional geometry along thelongitudinal axis (e.g. 3217 of FIGS. 3B, 3C and 3D) of the cavityadapted for receiving the blending, continuously transitioningcross-sectional geometry of the engagement end 2102 of the solid,monolithic shaft 2025. In other examples, the fastener cavity includesat least two different cross-sectional geometries (e.g., square anddiamond, torx and circle, rectangle and octagon, etc.).

The engagement end 2102 of the solid, monolithic shaft 2025 of FIG. 2inserts into a fastener cavity (e.g. 3215 of FIG. 3A). As shown in theexemplary fastener 3255 and engagement end 2102 assemblies of FIGS. 3Athrough 3D, the fastener 3255 is sized and shaped to accommodate theblending, continuously transitioning cross-sectional geometry of theengagement end 2102 so that fastener 3255 and engagement end 2102 aremated in a press fit or substantially press fit configuration. Theengagement end 2102 outside dimension 2125 is substantially equal to orless than the diameter of the fastener cavity 3215. In some examples,the cavity 3215 is sized to accommodate the blending, continuouslytransitioning cross-sectional geometry of the engagement end 2102 in apress fit, or substantially press fit, configuration such that theengagement end 2102 can deliver fastener 3255 while still enablingremoval of the solid, monolithic shaft 2025 from the cavity 3215following secured placement of the fastener 3255. This enables thesuccessful application of high torque (e.g., 3 in-lbf, 4 in-lbf, etc.)required to properly secure components, e.g. a sutured tendon to bone,while preventing the development of stress risers along the blending,continuously transitioning cross-sectional geometry of the engagementend 2102. By preventing stress risers, the solid, monolithic shaft 2025reliably deploys a fastener 3255 without breaking off in the fastener.Preventing such breakage eliminates the health risks and costsassociated with removal and replacement of the faster and suture.

FIGS. 3B, 3C, and 3D are cross-sectional views of the exemplaryfastener-shaft assembly 3000 of FIG. 3A cross-sectioned along lines B-B,C-C, and D-D respectively. As illustrated in FIG. 3B, the fastenercavity 3215 has a substantially circular cross-sectional shape 3215 a ata proximal end 3205 of the fastener 3255 (i.e., point (B-B) along thelongitudinal axis 3217). As illustrated in FIG. 3C, the fastener cavity3215 has a hybrid circle-triangle cross-sectional shape 3215 b at amidway point (C-C) along the longitudinal axis 3217, and as illustratedin FIG. 3D, the fastener cavity 3215 has a triangular cross-sectionalshape 3215 c at a distal end 3210 of the fastener 3255 (i.e., a point(D-D) along the longitudinal axis 3217).

As depicted in FIG. 4, in some examples, the engagement end 4102 of asolid, monolithic shaft 4025 has a yield strength ranging between175,000 psi and 250,000 psi, and in other examples, the engagement end4102 has a yield strength of 220,022 psi. This range of yield strengthsis three times greater than a legacy drive tool 5025 depicted in FIG. 5that incorporates an engagement end 5102 of continuous cross-sectionalgeometry that transitions rapidly at a taper or undercut 5105, forexample, into a larger geometry. Such a legacy drive tool 5025 typicallyfails under a torque load of 3 in-lbf, the torque required to secure asuture within an arthroscopic fastening anchor system comprising afastener (not shown) mated to an anchor (not shown) with a suturesecured therebetween. As FIG. 5 indicates, a stress riser occurs at thetransition point 5110 between the engagement end 5102 and the largerdiameter portion 5112 of the drive tool 5025, and adjacent the rapidtransition in geometry occurring at the taper 5105.

By eliminating rapid transitions in geometry, the solid, monolithicshaft 4025 addresses the issue of catastrophic failure that would leadto the engagement end 4102 snapping off of the solid, monolithic shaft4025 during deployment of a fastener (not shown). As the example of FIG.4 indicates, the solid monolithic shaft 4025 withstands 3 in-lbf oftorque without exhibiting concentrated stress risers that would lead tocatastrophic failure. The solid, monolithic shaft 4025 therefore enablesthe delivery and fastening of extremely small fasteners without thesolid, monolithic shaft 4025 breaking under torque load required, forexample, for proper suture fixation during arthroscopic surgery.

In some examples, such as the example of related FIGS. 2 and 3B, theoutside dimension 2125 of the distal end 2110 of engagement end 2102 isno more than 1.2 mm and the outside diameter 3230 of the fastener 3255is no more than 2 mm. In this example, the engagement end 2102 andfastener are no more than 10 mm long each as measured along longitudinalaxes 2115 and 3217. In this example, the delivery device comprising theengagement end 2102 and torque application end 120 is 16 inches long.Eliminating abrupt transitions in geometry therefore enables a solid,monolithic shaft 2025 to deliver a micro-scale fastener 3255 in a lowclearance area and apply sufficient torque (e.g., 3 in-lbf) to securesutures 1045 without catastrophic breakage of the delivery device (e.g.,1010 of FIG. 1A). The progressive transition in cross-sectional geometryallows for increased torsional strength of the delivery device anddecreased fastener diameter.

Another example is a fastening system 1000 including a solid, monolithicshaft member 1025 and a fastener 1055. In some examples, the solid,monolithic shaft member 1025 has an engagement end 2102, and theengagement end 2102 has a proximal end 2105 and a distal end 2110. Theproximal end 2105 has a first cross-sectional geometry 2107 and thedistal end 2110 has a second cross-sectional geometry 2112, and thefirst cross-sectional geometry 2107 of the proximal end 2105 isdifferent from the second cross-sectional geometry 2112 of the distalend 2110. The second cross-sectional geometry 2112 of the distal end2110 transitions to the cross-sectional geometry 2107 of the proximalend 2105 along a longitudinal axis of the solid, monolithic shaft member2025 providing a gradual, blending, continuously transitioningcross-sectional geometry along the entire length of the longitudinalaxis 2115 of the engagement end 2102 of the solid, monolithic shaftmember 2025. In examples, the fastener system includes a fastener 3255defining a longitudinal cavity 3215 of substantially the same shape asthe cross-sectional geometry of at least one of the proximal end 2105 orthe distal end 2110 of the engagement end 2102 of the solid, monolithicshaft member 1025.

In some examples, the second cross-sectional geometry 2112 of the distalend 2110 is in a shape of at least one of a triangle, a square, arectangle, a hex, a circle, an ellipse, a cross, and a torx. In someexamples, the cross-sectional geometry of the proximal end 2105 is in ashape of at least one of a triangle, a square, a rectangle, a hex, acircle, an ellipse, a cross, and a torx. In other examples, theengagement end 2102 of the solid, monolithic shaft member 2025 includesno abrupt transitions in cross-sectional geometries along thelongitudinal axis 2115.

As depicted in the illustrative examples of FIGS. 3A through 3D, thelongitudinal cavity 3215 of the fastener 3255 provides a blending,continuously transitioning cross-sectional geometry along thelongitudinal axis 3217 adapted for receiving the blending, continuouslytransitioning cross-sectional geometry of the engagement end 2102 of thesolid, monolithic shaft 2025. In examples, the longitudinal cavity 3215includes at least two different cross-sectional geometries along thelongitudinal axis 3217. In some examples, the cavity 3215 is sized toaccommodate the blending, continuously transitioning cross-sectionalgeometry of the engagement end 2102 of FIG. 2 in a press fit orsubstantially press fit configuration such that the engagement end 2102can deliver fastener 3255 while still enabling removal of the solid,monolithic shaft 2025 from the cavity 3215 following securing thefastener 3255.

Illustrated in FIG. 6 is an exemplary fastener 6055 for securing asuture including a body member 6202 having an exterior surface 6220 anddefining an interior cavity 6215. The exterior surface 6220 includes afixation element 6222. In one example, the fixation element 6222includes threads or barbs and threads; however it is possible that thefixation element 6222 may include only barbs. The interior cavity 6215of the exemplary fastener 6055 includes a longitudinal cavity having ablending, continuously transitioning cross-sectional geometry along thelongitudinal axis 6217 of the body member 6202. In some examples, thelongitudinal cavity 6215 includes at least two different cross-sectionalgeometries, as depicted in the illustrative examples of FIGS. 3A through3D. In the illustrated example, the cross-sectional geometry of thelongitudinal cavity 3215 progressively transitions from a circle-shapedcavity 3215 a to a triangle shaped cavity 3215 c. In some examples, suchas that of FIGS. 2 through 3D, the longitudinal cavity 3215 is adaptedfor receiving an engagement end 2102 of a solid, monolithic shaft 2025having a cross-sectional geometry of substantially the same shape as thelongitudinal cavity 3215.

In some examples, such as that of FIG. 6, the exterior surface 6220 ofthe fastener 6055 further includes at least one retention element (notshown). The retention element may be threads or barbs or a combinationof threads and barbs, for example. For the purposes of this technology,the retention element includes threads or barbs and threads; however itis possible that the retention element may include only barbs. Forexample, two thirds of the exterior surface (e.g., as measured along thelongitudinal axis) can be covered in a fixation element 6222 ofengagement threads and the remaining third can comprise a retentionelement of one or more retention barbs. In any example, the lack ofabrupt geometric transition along the solid, monolithic shaft (e.g. 2025of FIG. 2) of the delivery device (e.g. 1010 of FIG. 1A) enablesreduction in size of the deployed fastener 6055. Specifically, thegradual transition along the solid, monolithic shaft allows for areduction in outside diameter 6230 of the fastener 6055. This therebyallows for greater fixation strength because less volume of the fastener6055 is dedicated to applying torque and a greater volume is dedicatedto fixation strength (e.g., deeper threads).

Comprise, include, and/or plural forms of each are open ended andinclude the listed parts and can include additional parts that are notlisted. And/or is open ended and includes one or more of the listedparts and combinations of the listed parts.

One skilled in the art will realize the technology may be embodied inother specific forms without departing from the spirit or essentialcharacteristics thereof. The foregoing examples are therefore to beconsidered in all respects illustrative rather than limiting of thetechnology described herein. Scope of the technology is thus indicatedby the appended claims, rather than by the foregoing description, andall changes that come within the meaning and range of equivalency of theclaims are therefore intended to be embraced therein.

I claim:
 1. A delivery device, comprising: a solid, monolithic shaftmember having an engagement end, the engagement end having a proximalend a distal end, wherein: a) the proximal end has a firstcross-sectional geometry and the distal end has a second cross-sectionalgeometry, the first cross-sectional geometry of the proximal end beingdifferent from the second cross-sectional geometry of the distal end;and b) the cross-sectional geometry of the distal end transitions to thea cross-sectional geometry of the proximal end along a longitudinal axisof the engagement end of the solid, monolithic shaft member providing agradual, blending, continuously transitioning cross-sectional geometryalong the entire length of the longitudinal axis of the engagement endof the solid, monolithic shaft member.
 2. The delivery device of claim1, wherein the cross-sectional geometry of the distal end is in a shapeof at least one of a triangle, a square, a rectangle, a hex, a circle,an ellipse, a cross, and a torx.
 3. The delivery device of claim 1,wherein the cross-sectional geometry of the proximal end is in a shapeof at least one of a triangle, a square, a rectangle, a hex, a circle,an ellipse, a cross, and a torx.
 4. The delivery device of claim 1,wherein the cross-sectional geometry of the distal end is a shape of apolygon.
 5. The delivery device of claim 1, wherein the solid,monolithic shaft member comprises no abrupt transitions incross-sectional geometries along the longitudinal axis.
 6. The deliverydevice of claim 1, wherein the cross-sectional geometry of at least oneof the proximal end or the distal end has a shape adapted to mate with afastener cavity of substantially the same shape.
 7. The delivery deviceof claim 6, wherein the fastener cavity provides a blending,continuously transitioning cross-sectional geometry along thelongitudinal axis of the cavity adapted for receiving the blending,continuously transitioning cross-sectional geometry of the engagementend of the solid, monolithic shaft.
 8. The delivery device of claim 6,wherein the fastener cavity includes at least two differentcross-sectional geometries.
 9. The delivery device of claim 1, whereinthe engagement end has a yield strength ranging between 175,000 psi and250,000 psi.
 10. The delivery device of claim 9, wherein the engagementend yield strength is 220,022 psi.
 11. A fastening system, comprising:a) a solid, monolithic shaft member having an engagement end, theengagement end having a proximal end and a distal end, wherein: i. theproximal end has a first cross-sectional geometry and the distal end hasa second cross-sectional geometry, the first cross-sectional geometry ofthe proximal end being different from the second cross-sectionalgeometry of the distal end, and ii. the cross-sectional geometry of thedistal end transitions to the cross-sectional geometry of the proximalend along a longitudinal axis of the solid, monolithic shaft memberproviding a gradual, blending, continuously transitioningcross-sectional geometry along the entire length of the longitudinalaxis of the engagement end of the solid, monolithic shaft member; and b)a fastener defining a longitudinal cavity of substantially the sameshape as the cross-sectional geometry of at least one of the proximalend or the distal end of the engagement end of the solid, monolithicshaft.
 12. The fastening system of claim 11, wherein the cross-sectionalgeometry of the distal end is in a shape of at least one of a triangle,a square, a rectangle, a hex, a circle, an ellipse, a cross, and a torx.13. The fastening system of claim 11, wherein the cross-sectionalgeometry of the proximal end is in a shape of at least one of atriangle, a square, a rectangle, a hex, a circle, an ellipse, a cross,and a torx.
 14. The fastening system of claim 11, wherein the engagementend of the solid, monolithic shaft member comprises no abrupttransitions in cross-sectional geometries along the longitudinal axis.15. The fastening system of claim 11, wherein the longitudinal cavityprovides a blending, continuously transitioning cross-sectional geometryalong the longitudinal axis adapted for receiving the blending,continuously transitioning cross-sectional geometry of the engagementend of the solid, monolithic shaft.
 16. The fastening system of claim13, wherein the longitudinal cavity includes at least two differentcross-sectional geometries along the longitudinal axis.
 17. A fastenerfor securing a suture, comprising: a body member comprising an exteriorsurface and defining an interior cavity, wherein: the exterior surfaceincludes a fixation element; and interior cavity includes a longitudinalcavity having a blending, continuously transitioning cross-sectionalgeometry along the longitudinal axis of the body member.
 18. Thefastener of claim 17, wherein the longitudinal cavity comprises at leasttwo different cross-sectional geometries.
 19. The fastener of claim 17,wherein the longitudinal cavity is adapted for receiving an engagementend of a drive shaft having a cross-sectional geometry of substantiallythe same shape as the longitudinal cavity.
 20. The fastener of claim 17,wherein the exterior surface further comprises a retention element.